The concept of a free-electron laser is known and has been described. See, for example, "Observation of Stimulated Emission of Radiation by Relativistic Electrons in a Spatially Periodic Transverse Magnetic Field," by Luis R. Elias, William M. Fairbank, John M. J. Madey, H. Alan Schwettman, and Todd I. Smith, Physical Review Letters, Vol. 36, pp. 717-720, 29 Mar. 1976. In the free-electron laser, gain of the laser beam is produced by an electron beam passing through a linearly polarized magnetic wiggler. The gain of such a device, according to the equations given in the above-identified reference, is proportional to the product of magnetic flux density squared and the electron density. Gain is also determined by the number of periods and the length of the wiggler. In order to get high energy output from such devices, such as are conceived for producing laser beams with sufficient peak power to trigger a fusion reaction, very long wigglers have been required due to limitations on the achievable intensities of the magnetic fields. Permanent magnet wigglers are capable of supplying only up to two tesla. A superconducting helix has been used but could supply adequate field strength in only a thin annular gain region. The complexities of providing extended gain region superconducting coil pairs and of focusing the electron beam so that it does not spread or get off center along such a distance in passing lengthwise through the wiggler have made this type of device of little practical value as a compact electron beam wiggler. The high inductance of such arrangements makes rapid pulsing to high intensities impractical.
In copending application Ser. No. 526,743 filed Aug. 26, 1983 by the same inventor as the present application, there is described a high energy pulse laser in which an electron beam is generated by an explosive magnetic flux compression generator capable of producing very high energy electron beams of relatively short duration. The electron beam is merged with a laser beam and directed down the axis of a magnetic wiggler which produces a spatially periodic magnetic field which modulates the electron beam and causes it to interact with the photons of the laser beam to amplify the laser beam. In order to maximize the magnetic field in such a laser device, a high current is pulsed through the wiggler in synchronism with the firing of the explosive electron beam generator. However, conventional electromagnetic type wigglers have a high inductance and are not suitable for use with rapidly pulsed currents.